Our ability to explain and control the adhesion of Listeria monocytogenes to surfaces is limited by the lack of molecular-scale studies on how the surface biopolymers of L. monocytogenes affect their attachment to surfaces. My long-term goal is to understand the molecular mechanisms by which L. monocytogenes adheres to surfaces. The objective of this R03 application is to explore the molecular effect of bacterial surface biopolymers on the initial attachment of L. monocytogenes to surfaces. The central hypothesis of this application is that bacterial surface biopolymers are essential molecular components that strongly affect L. monocytogenes charge, hydrophobicity, and elasticity and thus their attachment to surfaces. I further hypothesize that epidemic strains of L. monocytogenes will display attachment behaviors and surface characteristics that differ from environmental strains. My hypothesis has been formulated in part due to my earlier work that pointed to the importance of bacterial surface polysaccharides in controlling the attachment of bacteria to surfaces. The rationale for the proposed research is that by understanding the rules governing adherence will point to novel and rationally designed control efforts;secondly, not all strains of L. monocytogenes are equally likely to cause epidemic outbreaks;thirdly, attachment to food surfaces is the first point in the contamination process where we can expect to find phenotypic differences between epidemic and environmental strains, and finally its results are expected to lead to a subsequent hypothesis-driven R01 application, designed to improve our understanding of the molecular mechanisms that control L. monocytogenes'adhesion to surfaces under various environmental conditions. Surface biopolymers will be investigated mainly using atomic force microscopy (AFM). AFM is unique due to its ability to measure adhesion in liquid media that mimics the environment in which bacteria survive and interact with surfaces. In addition to AFM, bacterial surface charge, hydrophobicity, and biopolymer composition will be assayed via electrophoresis, contact angle and colorimetric measurements, successively. The proposed research is significant because its results are expected to firstly, be a step forward towards establishing a molecular mechanism that explains how L. monocytogenes can attach to surfaces and thus bring research a step closer towards the development of effective tools that can be used in prevention, control, early diagnosis, and treatment of L. monocytogenes'infections;secondly, help in establishing, at the molecular level, criteria to reduce unnecessary recalls of food products;and thirdly, allow us to optimize the pH conditions under which RTE food products should be stored to minimize their contamination by L. monocytogenes. Finally, molecular approaches in investigating the relationship between bacteria and surfaces are new research techniques that can lead to a better fundamental understanding and control of bacterial adhesion. Successful completion of the proposed studies is expected to be a step forward towards establishing a molecular mechanism that explains how L. monocytogenes attach to surfaces. Such mechanism will likely bring research a step closer towards the development of effective tools that can be used in prevention, control, early diagnosis, and treatment of L. monocytogenes'infections. Secondly, the results of the proposed studies will help in establishing, at the molecular level, criteria to reduce unnecessary recalls of food products. Thirdly, the results of the proposed studies will allow us to optimize the pH conditions under which RTE food products should be stored to minimize their contamination by L. monocytogenes. Finally, molecular approaches in investigating the relationship between bacteria and surfaces are new research techniques that can lead to a better fundamental understanding and control of the bacterial adhesion phenomenon.